This invention relates to a method of stabilizing a rock structure comprising boring a hole, inserting in the borehole a tubular stabilizer that is slimmer than the borehole and expanding the tubular stabilizer to anchor in the borehole.
In U.S. Pat. No. 4,459,067, a rock stabilizer is shown which comprises a closed longitudinally folded tube which is pressurized to expand to anchor in the borehole. This bolt provides an outstanding anchoring and the accepted diameter range of the holes is extremely wide. However, the bolt is comparatively expensive.
In Canadian Pat. No. 1,171,310, a longitudinally folded rock stabilizer is shown which is expanded in the borehole by means of a mandrel that is forced into the stabilizer. The expansion of the stabilizer is comparatively complicated and requires a comparatively high force.
In U.S. Pat. No. 3,922,867 and 4,012,913 rock stabilizers are shown which comprise a tube with a longitudinal slot. The stabilizers are initially wider than the borehole and they are forced into the borehole. The insertion requires a force that is of the same magnitude as the anchoring, and the allowed diameter range for the holes is very narrow.
In U.S. Pat. No. 3,349,567, a rock stabilizer is shown which comprises a tube that is inserted in the borehole and then expanded at discrete points by pulsed magnetic fields induced by high voltage pulses in a coil in a probe that is temporarily inserted in the stabilizer. The anchoring will probably be poor.
It is an object of the invention to provide a method of stabilizing a rock structure that is fast and simple and makes a low total cost for stabilizers as anchored in the rock.